Lake Zone Agricultural Research and Development Institute
Lake Zone Agricultural Research and Development Institute
Nzuki I.,University of Pretoria |
Nzuki I.,International Institute Of Tropical Agriculture |
Katari M.S.,New York University |
Bredeson J.V.,University of California at Berkeley |
And 10 more authors.
Frontiers in Plant Science | Year: 2017
Genetic mapping of quantitative trait loci (QTL) for resistance to cassava brown streak disease (CBSD), cassava mosaic disease (CMD), and cassava green mite (CGM) was performed using an F1 cross developed between the Tanzanian landrace, Kiroba, and a breeding line, AR37-80. The population was evaluated for two consecutive years in two sites in Tanzania. A genetic linkage map was derived from 106 F1 progeny and 1,974 SNP markers and spanned 18 chromosomes covering a distance of 1,698 cM. Fifteen significant QTL were identified; two are associated with CBSD root necrosis only, and were detected on chromosomes V and XII, while seven were associated with CBSD foliar symptoms only and were detected on chromosomes IV, VI, XVII, and XVIII. QTL on chromosomes 11 and 15 were associated with both CBSD foliar and root necrosis symptoms. Two QTL were found to be associated with CMD and were detected on chromosomes XII and XIV, while two were associated with CGM and were identified on chromosomes V and X. There are large Manihot glaziovii introgression regions in Kiroba on chromosomes I, XVII, and XVIII. The introgression segments on chromosomes XVII and XVIII overlap with QTL associated with CBSD foliar symptoms. The introgression region on chromosome I is of a different haplotype to the characteristic “Amani haplotype” found in the landrace Namikonga and others, and unlike some other genotypes, Kiroba does not have a large introgression block on chromosome IV. Kiroba is closely related to a sampled Tanzanian “tree cassava.” This supports the observation that some of the QTL associated with CBSD resistance in Kiroba are different to those observed in another variety, Namikonga. © 2017 Nzuki, Katari, Bredeson, Masumba, Kapinga, Salum, Mkamilo, Shah, Lyons, Rokhsar, Rounsley, Myburg and Ferguson.
Legg J.P.,International Institute Of Tropical Agriculture |
Sseruwagi P.,Mikocheni Agricultural Research Institute |
Boniface S.,International Institute Of Tropical Agriculture |
Okao-Okuja G.,National Agricultural Crops Resources Research Institute |
And 10 more authors.
Virus Research | Year: 2014
The greatest current threat to cassava in sub-Saharan Africa, is the continued expansion of plant virus pandemics being driven by super-abundant populations of the whitefly vector, Bemisia tabaci. To track the association of putatively genetically distinct populations of B. tabaci with pandemics of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), a comprehensive region-wide analysis examined the phylogenetic relationships and population genetics of 642 B. tabaci adults sampled from cassava in six countries of East and Central Africa, between 1997 and 2010, using a mitochondrial DNA cytochrome oxidase I marker (780 bases). Eight phylogenetically distinct groups were identified, including one, designated herein as 'East Africa 1' (EA1), not previously described. The three most frequently occurring groups comprised >95% of all samples. Among these, the Sub-Saharan Africa 2 (SSA2) group diverged by c. 8% from two SSA1 sub-groups (SSA1-SG1 and SSA1-SG2), which themselves were 1.9% divergent. During the 14-year study period, the group associated with the CMD pandemic expansion shifted from SSA2 to SSA1-SG1. Population genetics analyses of SSA1, using Tajima's D, Fu's Fs and Rojas' R2 statistics confirmed a temporal transition in SSA1 populations from neutrally evolving at the outset, to rapidly expanding from 2000 to 2003, then back to populations more at equilibrium after 2004. Based on available evidence, hybrid introgression appears to be the most parsimonious explanation for the switch from SSA2 to SSA1-SG1 in whitefly populations driving cassava virus pandemics in East and Central Africa. © 2013 Elsevier B.V.
Masunga R.H.,Lake Zone Agricultural Research and Development Institute |
Masunga R.H.,Ghent University |
Uzokwe V.N.,International Institute Of Tropical Agriculture |
Mlay P.D.,Lake Zone Agricultural Research and Development Institute |
And 4 more authors.
Applied Soil Ecology | Year: 2016
Sustainable agriculture requires the careful optimization of the use of organic amendments to improve soil fertility while minimizing any harmful environmental effects. To understand the events that occur in soil after the addition of different organic amendments, we evaluated the nitrogen (N) mineralization dynamics in soil after adding organic amendments, and evaluated changes in the microbial population. The four organic amendments were fresh dairy cattle manure, fresh white clover, vegetable, fruit, and yard waste compost, and poplar tree compost. The N mineralization potential of each organic amendment was determined by analyzing total mineral nitrogen during a 97-day laboratory incubation experiment. Soils amended with clover released 240 μg N g-1 soil during the 97-day incubation, more than twice as much as that released from soils amended with manure or composts (76-100 μg N g-1 soil). At the end of the incubation, the net N mineralization in clover-amended soils was 54%, more than five times higher than that in soils amended with composts or manure (4%-9%). Nitrogen was mineralized faster in clover-amended soil (1.056 μg N g-1 soil day-1) than in soil amended with composts (0.361-0.417 μg N g-1 soil day-1). The microbial biomass carbon content was higher in clover-amended soil than in the soils amended with manure or composts. We monitored changes in the microbial population in amended soils by a phospholipid fatty acid (PLFA) analysis. On day 97, there were higher concentrations of total PLFAs in soils with organic amendments (e.g., 14.41 nmol g-1 in clover-amended soil) than in control soil without amendments (9.84 nmol g-1). Bacteria (Gram-positive and Gram-negative), actinomycetes, and fungi were more abundant in clover-amended soils than soils amended with manure or composts. The N mineralization potential varied among the four organic amendments. Therefore, the timing of application and the type of organic amendment should be matched to the nutrient needs of the crop. © 2016 Z.
PubMed | International Institute Of Tropical Agriculture, Maruku Agricultural Research Institute, Mikocheni Agricultural Research Institute, Lake Zone Agricultural Research and Development Institute and 7 more.
Type: | Journal: Virus research | Year: 2014
The greatest current threat to cassava in sub-Saharan Africa, is the continued expansion of plant virus pandemics being driven by super-abundant populations of the whitefly vector, Bemisia tabaci. To track the association of putatively genetically distinct populations of B. tabaci with pandemics of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), a comprehensive region-wide analysis examined the phylogenetic relationships and population genetics of 642 B. tabaci adults sampled from cassava in six countries of East and Central Africa, between 1997 and 2010, using a mitochondrial DNA cytochrome oxidase I marker (780 bases). Eight phylogenetically distinct groups were identified, including one, designated herein as East Africa 1 (EA1), not previously described. The three most frequently occurring groups comprised >95% of all samples. Among these, the Sub-Saharan Africa 2 (SSA2) group diverged by c. 8% from two SSA1 sub-groups (SSA1-SG1 and SSA1-SG2), which themselves were 1.9% divergent. During the 14-year study period, the group associated with the CMD pandemic expansion shifted from SSA2 to SSA1-SG1. Population genetics analyses of SSA1, using Tajimas D, Fus Fs and Rojas R2 statistics confirmed a temporal transition in SSA1 populations from neutrally evolving at the outset, to rapidly expanding from 2000 to 2003, then back to populations more at equilibrium after 2004. Based on available evidence, hybrid introgression appears to be the most parsimonious explanation for the switch from SSA2 to SSA1-SG1 in whitefly populations driving cassava virus pandemics in East and Central Africa.
News Article | December 12, 2016
UKIRIGURU, TANZANIA--(Marketwired - December 12, 2016) - Tanzania recently became a partner of the Next Generation Cassava Breeding project (NextGen), joining Nigeria and Uganda in the global effort to improve cassava breeding in Africa. This partnership is expected to enhance the project's efforts to improve livelihoods for African cassava farmers. "Partnering with NextGen should help us develop tools to address biotic stresses like cassava brown streak disease, cassava mosaic disease, and cassava green mite, and improve cassava root yields that will serve to increase cassava production countrywide," said Heneriko Kulembeka, cassava breeder and NextGen coordinator in Tanzania. "The NextGen project will assist in determining good parental lines for different traits of interest." "Tanzania has one of the foremost cassava breeding programs in Africa," said Chiedozie Egesi, NextGen manager of the Cornell University-led project. "Because Tanzania shares African cassava germplasm, they will benefit from the genomic predictions that NextGen has already developed, use of the NextGen Cassavabase database and capacity for improved phenotyping." Cassava is a vital crop in Tanzania, second only to maize in volume produced. More than 80 percent of farmers in the country grow cassava, producing about 4.5 million tons of cassava roots annually. About three-quarters of the crop is used for human consumption. The rest is used for livestock feed and industrial purposes. A widely preferred and hardy staple, cassava is often stored in the ground and locally processed as a source of food in times of famine. Cassava farmers face many challenges raising their crop. Tanzania loses an estimated 2.5 million tons each year to cassava brown streak disease, cassava mosaic disease, and cassava green mite. There is poor access to improved planting materials and processing technologies, limited use of fertilizers and herbicides, and low investment in cassava research and improvement. To address these challenges, researchers in Tanzania's Ministry of Agriculture, Livestock, and Fisheries (DRD) will collaborate with scientists on the NextGen project largely through ongoing efforts at the Lake Zone Agricultural Research and Development Institute (LZARDI), the oldest agricultural research station in Tanzania. LZARDI scientists are well prepared to contribute to the efforts of NextGen partners through cassava-related research that includes breeding and improvement, molecular marker-assisted breeding for disease resistance, processing and product development, and agronomy studies. The NextGen Tanzania team consists of Kulembeka; Kiddo Mtunda, cassava breeder and coordinator (coastal Tanzania); Geoffrey Mkamilo, national team leader of the Cassava Research Program in Tanzania; Kasele Salum, assistant cassava breeder (Lake Zone); and Caroline Sichwale, assistant cassava breeder (Eastern Zone). NextGen is a global partnership led by International Programs in the College of Agriculture and Life Sciences at Cornell University, in collaboration with the International Institute of Tropical Agriculture and National Root Crops Research Institute breeding centers in Nigeria, the National Crops Resources Research Institute in Uganda, DRD in Tanzania, the West African Centre for Crop Improvement in Ghana, Makerere University in Uganda, and the Boyce Thompson Institute, USDA-ARS, and the U.S. Department of Energy in the United States. The Cornell-led project is funded by a $25 million, five-year grant from the Bill & Melinda Gates Foundation and the Department for International Development of the United Kingdom, and is in its fourth year.
Hillocks R.,University of Greenwich |
Maruthi M.,University of Greenwich |
Kulembeka H.,Lake Zone Agricultural Research and Development Institute |
Jeremiah S.,Lake Zone Agricultural Research and Development Institute |
And 10 more authors.
Journal of Phytopathology | Year: 2016
Cassava brown streak disease is endemic to the coastal regions of East Africa, and from around 2004, the disease resurged and became epidemic in the Great Lakes Region, where it continues to spread. In both these areas, cassava brown streak disease (CBSD) leaf symptoms occur at high incidences. However, it is the associated symptom of root rot (necrosis) in the starch-bearing tissues that renders the root unfit for human consumption. Because the extent of root necrosis is not known until the crop is harvested and surveys require destructive sampling, root symptoms are much less frequently assessed than are the above-ground symptoms on the leaves and stems. Surveys were undertaken in selected villages in Tanzania, Kenya, Uganda and Malawi to assess the incidence of CBSD leaf symptoms and the incidence and severity of root symptoms, to estimate the impact of the disease on household food security and on cassava processing. CBSD leaf symptoms were recorded at high incidences (40-90% in individual fields) in all fields visited throughout East Africa, but root necrosis incidence was lower than would be expected from the high incidence of leaf symptoms. Severe root necrosis at high incidence was found only on a few varieties, usually grown to a limited extent. It appears that varieties that are prone to root necrosis are being abandoned in favour of those with a lower propensity to develop root necrosis after infection by the virus. © 2016 Blackwell Verlag GmbH.
Okello J.J.,International Potato Center |
Sindi K.,International Potato Center |
Shikuku K.,International Potato Center |
Low J.,International Potato Center |
And 5 more authors.
Agroecology and Sustainable Food Systems | Year: 2015
Efforts to combat vitamin A deficiency in children and pregnant mothers have focused on promotion of nutritionally enhanced food security crops. Such efforts have recently targeted the production and consumption of these crops. The orange-fleshed sweetpotato (OFSP) is one of the most known nutritionally enhanced crops. However, access to quality planting materials of OFSP and most vegetatively propagated crops by farmers remains a major constraint. This study used discrete and count data regression models and data collected from 732 farm households in Tanzania to test the effect of participation on a project designed to break this quality “seed” bottleneck (via technology awareness and targeted access to clean planting materials) on a) the decision to conserve planting materials during dry periods for future planting and b) the number of conservation strategies used by farmers. The study found that participation in such a project increases both the likelihood of conserving quality planting materials and also the number of conservation strategies employed by the farmers. It also found that varietal attributes and the agroecology of the area affect conservation of OFSP planting materials. It concludes that awareness and access to clean sweetpotato planting materials of nutritionally enhanced crops promote farmers. conservation of own planting materials. The study discusses the policy implications of the findings. Copyright © Taylor & Francis Group, LLC.